A typical photographic element contains multiple layers of light-sensitive photographic silver halide emulsions with one or more of these layers being spectrally sensitized to blue light, green light, or red light. The blue, green, and red light sensitive layers will typically contain yellow, magenta or cyan dye forming couplers, respectively.
For forming color photographic images, the color photographic material is exposed imagewise and processed in a color developer bath containing an aromatic primary amine color developing agent. Image dyes are formed by the coupling reaction of these couplers with the oxidized product of the color developing agent. Generally, image couplers are selected to provide image dyes with good stability towards heat and light and which desirably have a desirable absorption curve with a suitable peak absorption and low unwanted side absorptions in order to provide color photographic images with good color reproduction.
The couplers used to produce cyan image dyes are generally derived from phenols and naphthols, as described, for example, in U.S. Pat. Nos. 2,367,351, 2,423,730, 2,474,293, 2,772,161, 2,772,162, 2,895,826, 2,920,961, 3,002,836, 3,466,622, 3,476,563, 3,880,661, 3,996,253, 3,758,308, in French patents 1,478,188 and 1,479,043, and in British patent 2,070,000. These types of couplers can be used either by being incorporated in the photographic silver halide emulsion layers or externally in the processing baths. In the former case the couplers must have ballast substituents built into the molecule to prevent the couplers from migrating from one layer into another. Although these couplers have been used extensively in photographic film and paper products, the dyes derived from them still suffer from peak absorption wavelenghts that are too high and from undesirable side absorptions, causing considerable reduction in color reproduction.
Cyan couplers which have been so far proposed to overcome this problem are nitrogen containing heterocyclic couplers as disclosed in U.S. Pat. Nos. 4,728,598, 4,818,672, 4,873,183, 4,916,051, 5,118,812, 5,206,129, and EP patent 249,453A. Even though cyan dyes produced by these couplers show a reduction in their undesirable side absorptions, these couplers exhibit undesirably low coupling activity. Furthermore, the dyes derived from them have very low stability against heat, light, and have a very short absorption peak (.lambda.-max). These disclosed couplers are therefore not practical for use in photographic products.
Other cyan couplers proposed for improving color reproduction are disclosed in U.S. Pat. Nos. 3,552,962, 3,839,044, 4,960,685, and German patent publications DE 3,005,355 and 3,022,915. All these couplers are based on a well known coupler parent disclosed in U.S. Pat. No. 3,002,836 that is currently used in photographic color film products (see formula I). However, to use these couplers as incorporated couplers in the silver halide emulsion layers, and to achieve the same sharp-cutting dye hue as provided by coupler represented by formula (I), these couplers must by necessity be ballasted in the aryloxy coupling-off groups or be anchored to a suitable polymeric backbone as illustrated by formula (II). ##STR2##
While these latter couplers will form the same dye as those provided by formula (I), their color reproducibility is highly variable and highly dependent on the type and nature of the coupling-off groups, which, because of the ballasts, are not readily washed out of the photographic layers during processing.
U.S. Pat. No. 4,208,210 suggests couplers useful for forming dye that absorbs radiation in the infrared range above 725 nm. Two suggested compounds have the formula: ##STR3## Such couplers are not useful to form cyan dyes because of their high peak absorption wavelength at 725 nm would not provide the desired cyan color. Also, the desire to reduce the extent of undesired absorption in the magenta region is not relevant to an infrared dye and no mention is made of such concern in the patent.
U.S. Pat. No. 4,883,746 is a patent directed to masking coupler dye combinations. There are many example couplers showing a naphthol having a phenylcarbamoyl substituent in the 2-position. However, due to the lack of an ortho substituent on the phenyl ring and due to the substituent selection on the sulfamoyl group, the dye formed by the coupler does not exhibit the desired hue properties. An example of one of the disclosed couplers is: ##STR4##
It is a problem to be solved to provide a photographic element containing a cyan coupler which exhibits improved hue as evidenced by an absorption curve with reduced peak absorption wavelength and reduced side absorptions of the formed dye, particularly on the short wavelength side of the spectrum.